Dielectric rod antenna



Dec. 13, 1955 J. EYGES' 3,727,233

DIELECTRIC ROD ANTENNA Filed Dec. 11, 1945 INVENTOR LEONARD J. EYGES ATTORNEY DIELECTRIC ROD ANTENNA Leonard J. Eyges, Cambridge, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application December 11, 1945, Serial No. 634,298 4 Claims. (Cl. 343-785) This invention relates to an antenna, and more particularly to an antenna array of dielectric rods having directive properties such that the peak intensity of the main lobe is shifted oh the axis of the array.

Antennas for use with automatic tracking radar systems usually employ for the purpose of securing a conical scan either a paraboloid reflector having some means for displacing the feed with respect to the axis of the reflector, or a lobe-switching array of radiators with a means for changing periodically the relative phases of the currents exciting particular radiators in the array.

Antennas employing the feed-displacement method of scanning usually present a severe mechanical problem in dynamic balancing because of the large moment of inertia involved when a long paraboloid feed is revolved at a high rate of speed or when the reflector is revolved about an axis diiferent from its own axis.

Antennas of the lobe-switching type require the use of a switching or a phasing device capable of handling large amounts of radio frequency power at high rates of speed. One type of lobe-switching antenna which incorporates dielectric rods as radiating elements employs a probe inserted into each dielectric rod, together with suitable impedance matching means, to couple the energy from the transmission line to the radiating elements.

It is an object of this invention to provide an antenna array of dielectric rods excited directly by an electromagnetic horn.

It is a further object of this invention to provide an antenna array having a beam directed along an axis difierent from the axis of the array.

It is a further object of this invention to provide an antenna array having a high power gain and directivity consistent with a small aperture normal to the planes of the main lobe.

These and other objects will be more apparent upon consideration of the following description together with the accompanying drawings, in which Fig. 1 is an oblique cutaway view of an embodiment of this invention; and

Fig. 2 is a sectional view along line IIII of Fig. 1.

With particular reference to Figs. 1 and 2, a metal, compound electromagnetic horn 11 flared in two planes is connected at its throat to a waveguide transmission line 10. A rectangular metal box extension 13 is fastened to the mouth of the horn 11. Disposed at each corner of the box 13 are dielectric rod radiators 16, 17, 18 and 19 (19 not shown) having square bases. The rods are mechanically fastened in position by a rectangular block 14 of dielectric material having its corners cut away to accept the square bases of the rods.

Thin sheets 2t), 21, 22 and 23 of a suitable dielectric material are fastened between the rods to position and secure them.

The space within the horn between the horn throat and the bases of dielectric rods 16 and 17 is filled in part with a phasing section 12 of dielectric material.

States Patent Radio frequency energy introduced into the waveguide transmission line 10 will, under suitable conditions known to those familiar with the art, be propogated toward the horn throat and through the horn and dielectric rods into free space. Because of the difference in the velocity of propogation through the dielectric phasing section 12 between the horn throat and the rods 16 and 17 and that through the air between the horn throat and rods 18 and 19, the energy will arrive at the ends of rods 16 and 17 in a time phase diiferent from that at the ends of rods 18 and 19. Thus a plane of equal phase of the energy taken in a region near the ends of the rods would not be normal to the longitudinal axes of the rods but would be inclined, so that a line in the direction of the peak intensity of the main lobe of the array would be displaced with respect to the axis of the array. The amount and direction of such displacement, assuming a fixed position of the rods, is a function of the diflerence between the electrical path length in the air within the horn and in the dielectric phasing section 12.

The above described antenna can be rotated about its longitudinal axis to produce a conical scan if desired. Since the antenna can be made very nearly symmetrical about a central axis, the problem of dynamic balancing is relatively simple.

Lobe switching can be effected, if such is desired, by the installation of a mechanical arrangement whereby the dielectric phasing section 12 is shifted between alternate pairs of rods, thus changing the direction of the peak intensity of the beam in the manner described above.

Since certain changes may be made in the above described article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense, and therefore that the invention is to be limited only by the prior art and the spirit of the appended claims.

What is claimed is:

1. An antenna comprising, ductive electromagnetic horn, said horn being flared in two planes and being connected at its throat to said transmission line, a rectangular metal box fastened to the mouth of said horn, said box having an open end, four dielectric rod radiators having square bases, the base of each of said rods being fastened in a corner of said box, a rectangular block of dielectric material fastened to said rods and said box, the corners of said block being removed to accept the square bases of said rods, four sheets of dielectric material fastened between adjacent rods to fix the relative positions of said rods, and a phasing section of dielectric material disposed between the bases of two of said rods and the throat of said horn.

2. An antenna for producing a predetermined radiation pattern comprising a conductive electromagnetic horn flared in two planes, means for electrically coupling the throat of said horn to an external circuit, a plurality of dielectric rods, means for mechanically mounting said rods in rigid spaced relationship at the mouth of said horn in the direction of energy propagation, means for controlling the relative time phase of excitation of selected rods to displace the axis of directivity of energy propagation from the longitudinal axis of said horn.

3. An antenna comprising, an electromagnetic horn, means for electrically coupling the throat of said horn to an external circuit, a plurality of dielectric rods, means for mechanically mounting said rods parallel to the axis of said horn, said rods being positioned at the mouth of said horn for receiving radiation therefrom, and dielectric coupling means for controlling the phase of excitation of a transmission line, a conselected rods to'shift the axis of directivity of energy propagation from theaxis of said born.

4. An antenna for producing a predetermined radiation pattern comprising a conductive electromagnetic horn flared in-two planes, means'for electrically coupling the throat of said horn to an external circuit, a plurality of dielectric rods, means for mechanically coupling said rods perpendicular to the plane of the mouth of said horn, said rods being positioned at the mouth of said born for receiving radiation therefrom, and dielectric coupling means for controlling the phase of excitation of selected rods to control the relative time phase of the energy propagated by said selected rods whereby the axis of directivity of energy propagation is displaced.

References Cited in the file of this patent UNITED STATES" PATENTS Bowen Sept. 13, Southworth Sept. 13, King May 26, Barrow Oct. 13, Buchholz Mar. 7, Feldman et al. Dec. 3, Feldman Feb. 4, Becket a1 Mar. 4, 

